The subject disclosure relates to the printing arts, the copying/scanning arts, the image processing arts, the color processing arts, spot color printing, and the like.
While historically images were captured using photographic film, modern digital devices (such as scanners, cameras, etc.) capture images as pixels electronically, and most such digital devices capture images in a color space referred to as RGB, or red-green-blue color space. The RGB color space is utilized by image capture devices because such devices commonly include sensors that distinguish between the red, green, and blue colors.
When processing images captured by digital devices to make color corrections, remove undesirable artifacts, improve image resolution, suppress background, prepare images for printing or display, etc. (which is sometimes referred to as image path processing) it is often useful to first convert the electronic images into a color space that is device independent, such as the CIEL*a*b* color space.
The L*a*b* color space has an L dimension for lightness and a* and b* that are color-component dimensions (green-red and blue-yellow, respectively). The L*a*b* color space includes all perceivable colors, which means that its gamut exceeds those of the RGB and CMYK color spaces. The L*a*b* color space is device independent, which means that the colors are defined independent of their nature of creation or the device they are displayed on.
Printing devices generally operate in a smaller gamut color space, such as the RGB or CMYK color spaces, that are named based on the colors of the marking materials (e.g. inks, toners, etc.) used; such as red, green, and blue (RGB); or cyan, magenta, yellow, and black (CMYK). Thus, in order to print images represented in the L*a*b* color space, the image data must be transformed to either the RGB or CMYK color space.
Color space transformations using methods and formulae more complex than 1D look up tables, such as for example and without limitation tetrahedral interpolation, are one of the more computationally expensive functions in color image path for digital copiers and multifunction devices. In a software-based image path, it is desirable to reduce the amount of arithmetic processing and processing time of color space transformations in order to improve the overall system performance.
Accordingly, a method and system to improve color space conversion from L*a*b* to CMYK with increased efficiency, faster processing, and improved quality is needed.